That Beth Tweddle has had an extremely successful career is beyond doubt. Becoming a three-times world and seven-times national champion are achievements few are likely to match. However, what is perhaps most extraordinary is the sheer longevity of her time at the sharp end of gymnastic competition.

Tweddle is 27 and stands on the verge of her third Olympic Games. Her ability to continue at the highest level has been central to a fundamental change in the sport – the old order of female gymnasts having to peak at a specific age and time for their one shot at Olympic glory looks set finally to be shattered.

Tweddle's personal coach, Amanda Reddin, has seen the sport's transformation since competing on the floor at Los Angeles in 1984. She retired in 1985 after her only appearance at the Games, becoming a full-time coach a year later and has been working with Tweddle since 1997. Long enough for the two to form a special relationship, which has been crucial, Reddin says.

"Even at 27, she appreciates that basically what I say goes. Yes, she has an input, more of an input than she did five years ago, 10 years ago, but the relationship works because she still listens to me as her coach, but she's still determined and ambitious."

It has also worked for so long partly because Tweddle has competed for so long. Reddin says: "For women's gymnastics, Beth is pretty unique – still in the sport at this age. So obviously we've been together longer than most partnerships." But it has also meant more because of what it demonstrates to other gymnasts. "Because she's working hard and she's successful, it's just a great model for the rest of them – 'Look, this is how it's done.'"

She suffers setbacks – Tweddle will miss next week's European Championships after undergoing knee surgery but she is already recovering well – and simply comes back more determined. It is a combination of mental strength, ambition and sheer joy in the sport and it is central to the changes gymnastics has experienced.

Reddin explains that, traditionally: "Aged 17, 18 or 19 the trend is to peak, but times have moved on. Beth and a few others are responsible for that. They argue: 'I'm keeping going because who says I've got to pack up just because I'm 20 years old? Where's the rule book?' If they are happy with the workload and they can deliver, then carry on."

It is a rallying cry that has rung through Team GB's women's gymnastics. "We're lucky enough in the GB team that all these girls pretty much carried on from Beijing and have all got chances to make the team for 2012," Reddin says. "Which is unheard of really. I think they look at some of the older ones and think: 'Well they're carrying on. So why not?'"

So they stick at it and bring with them all the crucial experience perseverance provides. For these girls it means the performance, not the event, is all important. Of the dozen contenders fighting for the five spots at London, five competed at Beijing: Tweddle, Hannah Whelan (both coached by Reddin), Imogen Cairns, Becky Downie and Marissa King.

"Really now, we are looking at the 16-year-olds as babies, where normally they would be seen as only having a couple more years in the sport," Reddin says. "It's really good because with longer in the sport they gain so much more experience."

Nor is there any cosy favouritism shown to these old hands over the youngsters. In fact they are just provoking greater efforts from everyone, argues Reddin. "The older ones are keeping them out because they are still delivering. Which is not a bad thing at all. The youngsters are having to push the older ones, which is making them work even harder."

But ultimately it is performance that counts and if that is the case, an athlete's age becomes irrelevant.

"We've got the trial coming up and if the youngsters deliver and get the better scores, then they will make the team," she says.

It is not a trend limited to Great Britain either, being echoed around the world since the fall of the eastern bloc. "There will be quite a few gymnasts in the Olympic Games this time, from different countries, who were there four years ago. Which, a few cycles of Olympics ago, wasn't the norm. To do two Olympics you were one of the very few on the women's side," she says.

Of course, the will to continue competing is always boosted by success, a factor Reddin traces back to the arrival of the Romanian Adrian Stan as technical director for the women in 1992, saying: "We know a lot more about the sport – it's all driven from our technical director. He developed us into thinking that we can do this as coaches, rather than that we need foreign coaches to do it for us. The confidence we got from him has given us the confidence to pass on to the girls. He's seen it from beginning to end."

It is an end she could have barely imagined in 1984. "The fact that you were chosen as an Olympian and then you go to an Olympic Games is always going to be with you," she says, "The difference is we were just taking part then.

"Today I'm still overwhelmed. I still have to pinch myself as a coach because we actually go with great chances now. We don't just go to do our little bit for the qualification and then sit in the audience for the next five days." For Reddin, as gymnastics evolves around her, there is simply no better place to be.

"We really are in this sport," she says gleefully. "It's brilliant to see and I love being part of it."